A technology of acquiring a three-dimensional image using a capturing device is advancing. Depth information (depth map) is required for acquiring a three-dimensional image. Depth information is information that indicates a spatial distance and shows perspective information of a point with respect to another point in a two-dimensional image.
A method in which infrared (IR) structured light is projected to an object and light reflected from the object is interpreted to extract depth information is one of the methods of acquiring depth information. According to the method using IR structured light, there is a problem in that it is difficult to obtain a desired level of depth resolution for a moving object.
Meanwhile, a time-of-flight (TOF) method is gaining attention as a substitute technology for the method using IR structured light. According to the TOF method, a distance from an object is calculated by measuring a flight time, i.e., a time taken for emitted light to be reflected.
Generally, a camera according to the TOF method scans a front surface of an object with light and recognizes a motion of an area of interest within the object. In this case, when the size of the area of interest is smaller than that of the front surface of the object or the area of interest is far away from the camera, there is a problem in that the resolution of the area of interest decreases.